The standard folding baby buggy consists of two side frames separated by cross-bars and having a seat or cot mounted between them. Some push-chairs can have the two side frames moved together for folding (3-dimensional fold); others have the distance between the side frames fixed (2-dimensional fold). The standard form of side frame has a delta-shaped side frame, with a front sloping strut or bar with a front wheel at its bottom end and a handle at its top end, a rear sloping bar with a rear wheel at its bottom end and hinged at its top end to a point around the middle of the front sloping bar, and a base bar, linking the two sloping bars, which is roughly horizontal and located toward the bottom end of the rear sloping bar. The base bar is hinged at about its mid-point.
The side frame can then be folded by bending the base bar at its central hinge, with its two halves coming together, and bringing together the rear sloping bar and the bottom end of the front sloping bar.